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03/19/12 4:41 PM ET

Miller's body composition raised eyebrows

Prospect's conditioning tweaked so he can endure full season

LAKE BUENA VISTA, Fla. -- Top prospect Shelby Miller arrived in Spring Training noticeably trimmer after tailoring his offseason workouts to cut weight and body fat. That wasn't, however, exactly what the Cardinals wanted to see.

While pleased with the work Miller put in to stay in shape this winter, some within the organization were concerned that this new body composition could jeopardize Miller's durability. As a result, Miller, who is now in Minor League camp, has been given a new conditioning directive to get prepared for the rigors of a full season.

"Shelby reported to Spring Training in very good physical condition, having lost weight and with a low body fat, but that was not necessarily a goal that he was given heading into the offseason," farm director John Vuch said. "Now that he's back with our strength and conditioning staff, they're making sure the plan he's following is geared toward ensuring he's getting in peak shape for baseball purposes. Once he's back in his normal baseball condition, durability shouldn't be a concern, and our medical staff feels that he should be where he needs to be by the time the season opens."

Manager Mike Matheny has drawn a distinction between Jake Westbrook's decision to shed weight and Miller's choice to do so. Through a change in diet and exercise, Westbrook dropped about 20 pounds over the winter. The organization, though, had pushed Westbrook to do that, believing that slimming down would help Westbrook stay more consistent with his mechanics and improve his durability.

Westbrook had been at his heaviest last year, when he went 12-9 with a 4.66 ERA in 33 starts. He averaged fewer innings per start than he had in any season since moving exclusively into a starting role, and he hadn't posted that high of an ERA since 2002.

"He wanted to do something drastically different, and for him, it's worked," Matheny said. "For Shelby, it's going to be kind of yet to be determined how he holds up. Time will tell."

It was not disclosed how much weight Miller lost when he reported to camp. When it came to his body composition, the Cardinals were mostly content with status quo. The 6-foot-3 Miller weighed 195 pounds last season, a year in which he pitched a career-high 139 2/3 innings and posted a 2.77 ERA. Miller, the organization's Minor League Pitcher of the Year each of the past two seasons, made 25 combined starts in Class A and Double-A in 2011.

The year before, which was his first full professional season, Miller logged 104 1/3 innings and finished with a 3.62 ERA.

"He had a couple strong seasons and then comes in [with his] body fat way down. There's a balance there," Matheny said. "You have to be careful not to put yourself in a position where you're losing muscle mass during the season. If you're a starting pitcher and you're going to grind through the season, you better have some things stored up.

"Sometimes working hard isn't always working smart. I don't know exactly what Shelby did, but he certainly had a different body. It's just one of those things that a young player has to figure out what is best for him."

The Cardinals' strength and conditioning staff has been involved in the redirection of Miller's workout program for a while now. Matheny said that tweaks were made as soon as a member of that staff visited Miller this winter and saw what he was doing.

Miller was one of three non-roster players to be reassigned to Minor League camp last Wednesday, and he made his first Minor League spring appearance on Sunday. Pitching in a Double-A game, Miller allowed seven hits and four earned runs in three innings. He struck out four.

The fact that Miller pitched in a Double-A game does not necessarily mean that is headed to that level in April. He could begin the year in either the Double-A or Triple-A rotation.

Miller made two Grapefruit League appearances, both against the Nationals, before being sent out of big league camp. In those starts, he gave up six hits, two walks and four earned runs over 4 1/3 innings.

Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.